In article , Grant Erwin says...

Postulate a big air tank pressurized to 180 psi, with a long (long enough so
the air has time to cool to ambient) pipe to an ideal regulator which regulates
the pressure down to 90 psi. The regulator's output is a pipe of the same size
which is connected to a constant load. The cfm going into the regulator is
measured to be 10 cfm @ 180 psi. What cfm will come out of the regulator at
90 psi?

Don't do the problem in cubic feet, simply convert into number
of molecules (and for simplicity, perform it with nitrogen) that
you calculate using teh universal gas law.

So many molecules of nitrogen enter the regulator, the
same number leave it. If the temperature at the inlet and
outlet are the same, then the volume will scale inversely
like the pressure.

P(1) X V(1) = P(2) X V(2)

Pressure goes down by a factor of two, the
volume will increase by two.

The pressures btw should be absolute, not gage, not
a problem to do in psig if the pressures are high.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================